U.S. Senator Paul Wellstone has a mild form of multiple sclerosis, the Minnesota Democrat announced Sunday.

Wellstone was diagnosed a month ago, but his doctor said he has probably had the disease for about 15 years. It would not affect his campaign for a third senate term, Wellstone said at his home, with his wife and doctor sitting next to him.

"Nothing's changed at all," he said. "I'm ready to go."

The disease only affects Wellstone's right leg, and he will not need to take any medication, said his physician, John Bartleson of the Mayo Clinic.

Bartleson said Wellstone can proceed with his normal day-to-day activities and that the stress of a senate campaign should not pose a problem for the two-term senator.

Wellstone is seeking a third senate term and faces a strong challenge from former St. Paul Mayor Norm Coleman, a Republican.

A recent poll showed the candidates in a dead-heat, and Wellstone said he was not worried about the stresses of a tight campaign.

"For me, no stress would be stress," he said.

Bartleson said the primary progressive multiple sclerosis is progressive but not fatal and wouldn't shorten Wellstone's life. The problem was confined to the motor system in the senator's lower right leg, Bartleson said.

Unlike other forms of the disease that can be helped by medication, no specific treatment has been found for the type Wellstone has.

The Senator said he decided to go public with the news because he wanted to be honest with people.

For years, people have asked him why he limps. He always told them it was an old athletic injury.

"I don't want to be dishonest with anyone," he said. "I can no longer say it was a wrestling injury because it is not."